Gentlemen, I have a 686-0 with a sn prefex of AAC66XX, This would put in the first group of 686's made. It is a 2.5 inch barrel with a sq butt. This gun has the M stamp and is a very good shooter. I had alyways thought that the 2.5 inch gun did not come out till the -3, much later. I bought this gun used about ten years ago and thought someone before me had rebarreled it. The workmanship is flawless which made me wonder about it's past history. . So now you're saying this might be a Lew Horton and correct. It looks as if I might be needing to send some money to Mr. Jinks for a letter. Anyone have any ideas, thoughts or comments? Captain Hornet